The present invention relates to the novel crystal Forms III, IV, V, and the amorphous form of clopidogrel hydrogensulfate, novel processes for their preparation, compositions containing the new forms and novel processes for the preparation of Form I.
Atherosclerosis is the buildup of plaque in the wall of the arteries leading to a thickening and a reduction in elasticity of the arteries. Atherosclerosis results from injury to the inside layer of the artery. The injury is caused by common activities and diseases such as high cholesterol, high blood pressure, smoking and infection.
Plaques form on the inner walls of the artery at these sites of injury. The plaques are mainly composed of fatty tissue and smooth muscle cells. The formation of plaque often leads to blood clotting due to platelet aggregation at the site of the injury. This clotting may result in a reduction or elimination of blood flow to vital organs, causing heart attacks or other serious conditions. The plaque may also rupture and send a blood clot through the artery, referred to as an embolus, which if deposited in a smaller blood vessel may completely block blood flow.
Antiplatelet activity is desirable in fighting the often fatal results of atherosclerosis. Clopidogrel is an inhibitor of induced platelet aggregation which acts by inhibiting the binding of adenosine diphosphate to its receptor. Clopidogrel is metabolized by the liver into active form. Its antiplatelet activity is extended in that it stops any platelet activity even up to ten days after administration.
The chemical name of clopidogrel is methyl (+)-(S)-xe2x88x9d-(o-chlorophenyl)-6,7-dihydrothieno[3,2-c]pyridine-5(4H)-acetate. It has the following structure: 
Clopidogrel""s platelet inhibiting activity makes it an effective drug for reducing the incidence of ischemic strokes, heart attacks or claudication due to vascular diseases such as atherosclerosis. By inhibiting platelet aggregation, clopidogrel reduces the chance of arterial blockage, thus preventing strokes and heart attacks. U.S. Pat. No. 5,576,328 describes a method of preventing the occurrence of a secondary ischemic event by administration of clopidogrel, and is incorporated herein as a reference.
Recent studies have shown that clopidogrel is more effective in blocking platelet aggregation than aspirin and is much gentler on the gastrointestinal tract. Clopidogrel is more effective than aspirin even at much lower dosage. A dosage of 75 mg of base equivalent has been shown to be more effective than a dosage of 325 mg of aspirin. In addition to being more effective, clopidogrel produces much less gastrointestinal bleeding than aspirin.
Clopidogrel is administered as its hydrogensulfate (syn. bisulfate) salt. Clopidogrel hydrogensulfate has an empirical formula of C16H16ClNO2S.H2SO4. It is currently being marketed as PLAVIX(copyright) tablets, which contain about 98 mg clopidogrel hydrogensulfate, which is the equivalent of 75 mg clopidogrel base. PLAVIX(copyright) is a white to off-white powder that is practically insoluble in water at neutral pH but highly soluble at acidic pH. It dissolves freely in methanol, somewhat in methylene chloride, and poorly in ethyl ether.
U.S. Pat. Nos. 4,847,265; 5,132,435; 6,258,961; 6,215,005 and 6,180,793, which are hereby incorporated by reference in their entirety, describe methods that can be used to prepare clopidogrel hydrogensulfate.
The present invention relates to the solid state physical properties of clopidogrel hydrogensulfate prepared by any of these or other methods. These properties can be influenced by controlling the conditions under which clopidogrel is obtained in solid form. Solid state physical properties include, for example, the flowability of the milled solid. Flowability affects the ease with which the material is handled during processing into a pharmaceutical product. When particles of the powdered compound do not flow past each other easily, a formulation specialist must take that fact into account when developing a tablet or capsule formulation, which may necessitate the use of glidants such as colloidal silicon dioxide, talc, starch or tribasic calcium phosphate.
Another important solid state property of a pharmaceutical compound is its rate of dissolution in aqueous fluid. The rate of dissolution of an active ingredient in a patient""s stomach fluid can have therapeutic consequences because it imposes an upper limit on the rate at which an orally-administered active ingredient can reach the bloodstream. The rate of dissolution is also a consideration in formulating syrups, elixirs and other liquid medicaments. The solid state form of a compound may also affect its behavior on compaction and its storage stability.
These practical physical characteristics are influenced by the conformation and orientation of molecules in the unit cell, which defines a particular polymorphic form of a substance. The polymorphic form may give rise to thermal behavior different from that of the amorphous material or another polymorphic form. Thermal behavior is measured in the laboratory by such techniques as capillary melting point, thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC), and can be used to distinguish some polymorphic forms from others. A particular polymorphic form may also give rise to distinct properties that may be detectable by powder X-ray diffraction, solid state 13C NMR spectrometry and infrared spectrometry.
The discovery of new crystalline forms of a pharmaceutically useful compound provides a new opportunity to improve the performance characteristics of a pharmaceutical product. It enlarges the repertoire of materials that a formulation scientist has available for designing, for example, a pharmaceutical dosage form of a drug with a targeted release profile or other desired characteristic.
U.S. Pat. No. 4,529,596 is directed to the composition of clopidogrel and methods of its use. The ""596 patent teaches synthesis of clopidogrel, but fails to suggest or disclose the existence of polymorphs or the amorphous form of clopidogrel. U.S. Pat. No. 4,847,265 is directed to the enantiomer of clopidogrel, and also does not suggest or teach any polymorphs or the amorphous form of clopidogrel. These U.S. patents are incorporated herein by reference.
International Publication No. WO 99/65915 discloses two polymorphs of clopidogrel hygrogensulfate, referred to as Forms I and II, though Form I is originally disclosed in EP 281459.
According to the International Publication No. WO 99/65915, Form I has a PXRD pattern with peaks at 9.2, 10.9, 15.2, 17.9, 18.5, 20.6, 23.0, 23.2, 23.4 and 25.5xc2x10.2 degrees two theta. Form I also has an infrared spectrum with absorption bands at 2987, 1753, 1222, 1175 and 841 cmxe2x88x921.
WO 99/65915 also discloses clopidogrel hydrogensulfate Form II, according to which has a PXRD pattern with peaks at 12.9, 13.6, 15.6, 17.7, 19.5, 21.6, 23.0, 23.3 and 24.7xc2x10.2 degrees two theta. It has an infrared spectrum with absorption bands at 2551, 1753, 1497, 1189 and 1029 cmxe2x88x921.
According to Applicants"" English translation, in Example 1B, Form I is prepared by dissolving clopidogrel camphorsulphonate in dichloromethane under a nitrogen atmosphere. A solution of potassium carbonate in water is then introduced. The organic phase is then removed, concentrated and added to acetone. The acetone solution is placed in a reactor under nitrogen and a 80% solution of sulfuric acid is added. The mixture is then distilled and cooled, followed by subsequent crystallization. The crystals are washed and dried to obtain Form I.
According to Chemical Abstract Accession No. 1999:811251, Form II is prepared by addition of a solution of 50 g of clopidogrel camphorsulfonate in 100 mL of dichlormethane to a solution of 9.1 g of potassium carbonate in 70 mL of water. The organic phase was separated, concentrated and dissolved in 229 mL of acetone. The acetone solution was refluxed with 7.4 g of 80% sulfuric acid under nitrogen for 2 h. The solvent was then removed to yield Form II.
Form II may also be prepared from Form I by storing aqueous mother liquor from the crystallization of Form I for 3-6 months.
Three new crystal forms of clopidogrel hydrogensulfate, designated Forms III, IV and V, plus the amorphous form of clopidogrel hydrogensulfate, and a novel process for their preparation, and preparation of Form I of clopidogrel have now been discovered.
In a first aspect, the present invention provides a new polymorph of clopidogrel hydrogensulfate, denominated Form III, and a process for its preparation. In another aspect, the present invention provides for clopidogrel hydrogensulfate characterized by a differential scanning calorimetric thermogram having an endothermic peak at about 105xc2x0 C. The present invention further provides for clopidogrel hydrogensulfate characterized by a powder X-ray diffraction pattern with peaks at about 8.1, 8.7, 14.3, 15.4, 20.1, 22.3, 22.5, 23.5, and 24.1xc2x10.2 degrees two theta. The present invention also provides for clopidogrel hydrogensulfate characterized by a FTIR spectrum with peaks at about 581, 707, 755, 971, 1057, 1196, 1252, 1436, 1476, 1748, 2590, 2670 and 2963 cmxe2x88x921.
In another aspect, the present invention provides for a process for preparing clopidogrel hydrogensulfate Form III comprises the steps of preparing a solution of clopidogrel hydrogensulfate in 1-butanol, removing the 1-butanol from the solution to obtain a residue, adding an antisolvent to the residue to cause formation of a precipitate, separating the precipitate and drying the precipitate.
The present invention also provides for the new composition of the amorphous form of clopidogrel hydrogensulfate. The present invention further provides clopidogrel hydrogensulfate characterized by a FTIR spectrum with peaks at about 583, 723, 762, 846, 1040, 1167, 1223, 1438, 1478, 1638, 1752, 2585 and 2960 cmxe2x88x921. In another aspect, the present invention provides for clopidogrel hydrogensulfate having a PXRD pattern as substantially depicted in FIG. 4.
In another aspect, the present invention provides a process for preparing the amorphous form of clopidogrel hydrogensulfate comprising the steps of preparing a solution of clopidogrel hydrogensulfate in an alcohol selected from the group consisting of methanol and ethanol, adding the solution to an antisolvent to cause formation of a precipitate and separating the precipitate.
In another aspect, the present invention provides a process for preparing the amorphous form of clopidogrel hydrogensulfate comprising the steps of preparing a solution of clopidogrel hydrogensulfate in an alcohol selected from the group consisting of methanol and ethanol, removing the alcohol from the solution to obtain a residue, adding an antisolvent to the residue to cause formation of a precipitate and separating the precipitate.
In another aspect, the present invention provides a process for preparing the amorphous form of clopidogrel hydrogensulfate comprising the steps of preparing a solution of clopidogrel hydrogensulfate in an alcohol selected from the group consisting of methanol and ethanol, adding the solution to an antisolvent and removing the alcohol and the antisolvent.
In another aspect, the present invention provides a process for preparing the amorphous form of clopidogrel hydrogensulfate comprising preparing a solution of clopidogrel hydrogensulfate in acetone and removing the acetone.
In another aspect, the present invention provides a process for preparing clopidogrel hydrogensulfate Form I comprising the steps of contacting amorphous clopidogrel hydrogensulfate with an ether and separating the clopidogrel hydrogensulfate Form I.
In another aspect, the present invention relates to clopidogrel hydrogensulfate Form IV. The present invention further provides clopidogrel hydrogensulfate characterized by a PXRD pattern with peaks at about 22.0, 25.9, 26.9, 27.4, 28.1, 28.6 and 28.9xc2x10.2 degrees two theta. In another aspect, the present invention provides clopidogrel hydrogensulfate characterized by a DTG thermogram with an endothermic peak at about 160-170xc2x0 C. The present invention further provides for clopidogrel hydrogensulfate characterized by a FTIR spectrum with peaks at about 618, 769, 842, 893, 935, 974, 1038, 1116, 1370, 1384 cmxe2x88x921.
In another aspect, the present invention provides a process for preparing clopidogrel hydrogensulfate Form IV comprising forming a precipitate from a solution of clopidogrel hydrogensulfate and isopropanol and separating the precipitate.
In another aspect, the present invention relates to clopidogrel hydrogensulfate Form V. The present invention also provides for clopidogrel hydrogensulfate characterized by a PXRD diffraction pattern with peaks at about 25.5, 26.6, 27.8 and 28.5xc2x10.2 degrees two theta. The present invention further provides for clopidogrel hydrogensulfate characterized by a DSC profile with an endothermic peak at about 126-132xc2x0 C. The present invention also provides for clopidogrel hydrogensulfate characterized by a FTIR spectrum with peaks at about 623, 743, 802, 817, 843, 963, 972, 1028 and 1374 cmxe2x88x921.
The present invention provides a process for preparing clopidogrel hydrogensulfate Form V comprising the steps of dissolving clopidogrel hydrogensulfate in 2-butanol to form a solution, adding an antisolvent to the solution to cause formation of a precipitate and separating the precipitate.
In another aspect, the present invention provides a process for preparing clopidogrel hydrogensulfate Form V comprising the steps of dissolving clopidogrel hydrogensulfate in 2-butanol to form a solution, removing the 2-butanol from the solution to obtain a residue, adding an antisolvent to the residue to cause formation of a precipitate and separating the precipitate.
The present invention also provides for pharmaceutical compositions of clopidogrel and methods of their use in order to inhibit platelet aggregation.